Air release valve delivery information

Large Size Double Orifice Air Valves — DN200 / DN300

Past DN200, an air valve stops being a fitting. It becomes a structural part of the main.

The pressure class does not change. DN200 and DN300 both carry PN16 — the same 16 bar. But the load on the flanged end does not scale with the pressure, it scales with the bore squared: DN200 → ~50 kN of end thrust DN300 → ~113 kN That second number is about 11 tonnes trying to push the valve off the pipe. One DN300 carries as much as 2.3 DN200s, or 14 of our DN80 units. Nothing about the pressure rating got bigger; the area did. That is why the DN300 is not an enlarged DN200. It is its own casting, and the differences run right through it: Wall section. More bolts do not recover a thin casting. At 113 kN the body has to carry the load, and the section behind the flange is what carries it. Fasteners. Twelve bolts on both sizes, but ⌀28 on M24 at DN300 against ⌀23 on M20 at DN200 — the bolting steps up with everything else. Handling. At DN300 the unit is a two-man lift at minimum. Lifting points and the sequence of installation matter more than the finish. Packing. Four DN300 to a plywood case, nine DN200 to the same case, in a cardboard grid so nothing touches in transit. The function is unchanged. Both sizes are double orifice: the large orifice under the hood vents the main during filling and admits air on drain-down so the pipe is not sucked flat, while the small orifice in the side chamber bleeds off the air that keeps leaving solution while the line is under pressure. Every body is cast in GGG50 ductile iron, epoxy coated inside and out, and carries its month of manufacture cast into the metal — 202610 on this batch. Ten years on, the age of the valve can still be read off the body.

Sized for the load At PN16 a DN300 flange carries ~113 kN. Wall section and bolting are sized to that, not to a nameplate. Two orifices, one body Large orifice for filling and draining; small orifice for continuous release under pressure. GGG50 ductile iron ISO 1083 / EN 1563 GJS-500-7, ≥500 MPa tensile, ≥7% elongation. It deforms before it cracks. Readable at year ten Month of manufacture cast into the body, so age is legible without a label.